Method for detecting HIV-1-specific antibodies using clade C env polypeptides

ABSTRACT

The present invention relates to a method for detecting and/or quantifying human immunodeficiency virus (HIV) specific antibodies in a sample of a subject comprising the step of determining the presence and/or amount of antibodies binding to a) a peptide consisting of the amino acid sequence AIVCTRPNNNTRKSIRIGPGQVFYT (SEQ. ID No. 1), or b) a homolog having at least 70% identity with a peptide of a), or c) a fragment of a peptide of a) or b) consisting of 15 to 24 amino acid residues in said sample.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser. No. 14/775,813, filed Sep. 14, 2015, which is the United States national phase of International Application No. PCT/EP2014/055194 filed Mar. 14, 2014, and claims priority to European Patent Application No. 13159417.8 filed Mar. 15, 2013, the disclosures of which are hereby incorporated in their entirety by reference.

The Sequence Listing associated with this application is filed in electronic format via EFS-Web and is hereby incorporated by reference into the specification in its entirety. The name of the text file containing the Sequence Listing is 159619_ST25.txt. The size of the text file is 23,068 bytes, and the text file was created on Jan. 15, 2018.

The present invention relates to means and methods for diagnosing a human immunodeficiency virus (HIV) infection in a subject.

Human immunodeficiency virus (HIV) is an enveloped RNA, virus and represents the etiological agent of the acquired immunodeficiency syndrome (AIDS). In the course of this disease the immune system is progressively destroyed so that already minor microbiological infections may end fatally. It is widely acknowledged that early diagnosis of an HIV infection is important in order to start at an early point in time with the antiviral treatment. This will improve the prognosis of the affected subject (in terms of morbidity and mortality) and reduce the onward transmission of the virus. Furthermore it is also beneficial to monitor the progress of the disease and the effect of the treatment. The detection of antibodies directed to HIV is presumptive evidence of an infection and is usually confirmed by Western blot procedures or by the detection of viral RNA by RT PCR or of viral protein.

In Casseb et al. (Brad J Med Biol Res 35 (2002): 369-375) synthetic peptides derived from the V3 region of the HIV-1 gp120 protein are disclosed.

Novitsky et al. (J Virol 76 (2002): 10155-10168) describe the identification of immunodominant regions of HIV-1 subtype C.

In Riabinina et al. (Mol Gen Mikrobiol Virusol 3 (2007): 33-36) it was discovered that the peptide corresponding to the V3 region gp120 of HIV-1 subtype C showed the highest immunoreactivity.

Cardozo et al. (AID Res Human Retrovir 25(2009): 441-450) investigated the worldwide distribution of HIV Type 1 epitopes recognized by human anti-V3 monoclonal antibodies.

Brennan et al. (J Medi Virol 78 (2006): S24-S29) is a review article about the difficulties in the development of valuable assays which can be used in detecting HIV infections in individuals.

Difficulties in the detection of antibodies directed to HIV reside in the fact that HIV has a high genetic variability. For instance, HIV type 1 (HIV-1), which is the most common and pathogenic type of the virus, can be divided in several groups and these groups are further divided in various subtypes also known as clades (e.g. group M comprises subtypes A to K). This genetic diversity makes it difficult to provide a diagnostic tool which allows diagnosing HIV more than one subtype in patients having an HIV infection. This means that one test system may be useful to diagnose an HIV subtype A infection but cannot be used to diagnose a HIV subtype D infection.

Therefore it is an object of the present invention to provide methods and means to diagnose HIV infections of more than one subtype.

The present invention relates to a method for diagnosing a human immunodeficiency virus (HIV) infection in a subject comprising the steps of determining the presence of antibodies binding to

-   -   a) a peptide consisting of the amino acid sequence         AIVCTRPNNNTRKSIRIGPGQVFYT (SEQ ID. No. 1), or     -   b) a homolog having at least 70% identity with a peptide of a),         or     -   c) a fragment of a peptide of a) or b) consisting of 15 to 24         amino acid residues,

in a sample of the subject, and diagnosing an HIV infection in said patient when the presence of such antibodies in said sample is determined or diagnosing no HIV infection in said patient when the absence of such antibodies in said sample is determined.

It surprisingly turned out that peptide fragments and homologs thereof derived from the envelope protein gp120 of HIV subtype C can be used to diagnose HIV infections of more than one, preferably of more than two, preferably of more than three, more preferably of more than four, more preferably of more than five, more preferably of more than six, more preferably of more than seven, even more preferably of more than eight, HIV subtypes since antibodies directed to gp120 of all these subtypes and obtainable from subjects having a HIV infection bind to a peptide consisting of the amino acid sequence AIVCTRPNNNTRKSIRIGPGQVFYT (SEQ ID No. 1) or a homolog or a fragment thereof consisting of 15 to 24 amino acid residues. Hence, the method of the present invention allows to diagnose HIV infection of HIV subtypes A, B, C, D, F, G, H, J, and/or K, whereby the diagnosis of HIV subtypes B and C is most preferred.

The method of the present invention allows diagnosing an HIV infection and to detect antibodies in an individual although other established conventional assays fail (see examples and FIG. 4). This is a rather surprising finding since it shows that the use of methods known in the art for the diagnosis of HIV infections in individuals is not really fully reliable.

The method of the present invention can also be used to diagnose that a subject has no HIV infection if the presence of the aforementioned antibodies cannot be determined in a sample of the subject.

Suitable fragments of AIVCTRPNNNTRKSIRIGPGQVFYT (SEQ ID No. 1) and/or LLGLWGCSGKLICTTAVHWNSSWSN (SEQ ID No. 2) or a homolog having at least 70% identity to SEQ ID No. 1 and/or 2 to be used in the present invention consist of 15 to 24, preferably 16 to 24, amino acid residues of SEQ ID No. 1 and/or 2, respectively. These fragments may consist of amino acid residues 1 to 23, 1 to 22, 1 to 21, 1 to 20, 1 to 19, 1 to 18, 1 to 17, 1 to 16, 1 to 15, 2 to 24, 2 to 23, 2 to 22, 2 to 21, 2 to 20, 2 to 19, 2 to 18, 2 to 17, 2 to 16, 3 to 24, 3 to 23, 3 to 22, 3 to 21, 3 to 20, 3 to 19, 3 to 18, 3 to 17, 4 to 24, 4 to 23, 4 to 22, 4 to 21, 4 to 20, 4 to 19, 4 to 18, 5 to 24, 5 to 23, 5 to 22, 5 to 21, 5 to 20, 5 to 19, 6 to 24, 6 to 23, 6 to 22, 6 to 21, 6 to 20, 7 to 24, 7 to 23, 7 to 22, 7 to 21, 8 to 24, 8 to 23, 8 to 22, 9 to 24, 9 to 23, 9 to 22, 2 to 25, 3 to 25, 4 to 25, 5 to 25, 6 to 25, 7 to 25, 8 to 25, 9 to 25, or 10 to 25 of SEQ ID No. 1 and/or 2.

The presence of antibodies in a sample can be determined using methods known in the art (e.g. immunoassays such as ELISA). For instance, one or more of the peptides of the present invention can be immobilized on a solid support. The solid support is then contacted with the sample comprising antibodies of the subject who is suspected to have an HIV infection. Antibodies able to bind to the peptides of the present invention will be immobilized on the solid support. These immobilized antibodies can be detected by using other antibodies, for instance, antibodies which are directed to one or more of the antibody isotypes IgA, IgG, IgG1, IgG2, IgG3, IgG4, and/or IgM.

The presence of antibodies directed to HIV-derived peptides and/or polypeptides in a sample of a subject indicates that said subject has an HIV infection. The absence of antibodies directed to HIV-derived peptides and/or polypeptides in a sample of a subject indicates that said subject has no HIV infection. IgM antibodies occur in higher amounts during acute infection, and their presence in human samples (e.g. serum, plasma) is used to diagnose early infections. IgG antibodies are low at early infection stages, but occur in patients during established infections. Most antibody-based HIV-diagnostic tests detect the presence of HIV-specific IgG in human samples (e.g. serum, plasma). IgA is a marker of mucosal immunity and can be detected in human secretes such as saliva, tears, etc., as well as in serum. Such antibodies are known to a person skilled in the art.

In order to facilitate the immobilization of the polypeptides and peptides of the present invention on a solid support it is advantageous to add to the C- and/or N-terminal end of said polypeptides and peptides cysteine residues or other moieties (e.g. linkers or carrier proteins, biotin, nucleic acids). This allows a facilitated attachment of the peptides and/or polypeptides on a solid support. Methods and means to attach peptidic molecules on a solid support are well known to a person skilled in the art.

“Human immunodeficiency virus (HIV)”, as used herein, refers to the HIV type 1 (HIV-1).

As used herein the term “subject” can be used interchangeably with “human individual”, “human”, or “individual”.

A “homolog having at least 70% identity with a peptide” or “homolog”, as used herein, refers to peptides which have at least 70%, preferably at least 75% identity, more preferably at least 80% identity, even more preferably at least 85% or 90% or 95% identity, with a peptide consisting of an amino acid sequence as defined herein (any one of SEQ ID Nos. 1 to 41), e.g. consisting of the amino acid sequence AIVCTRPNNNTRKSIRIGPGQVFYT (SEQ ID No. 1) or LLGLWGCSGKLICTTAVHWNSSWSN (SEQ ID No. 2). Sequence identity is determined by BLAST alignment (Altschul S F et al J. Mol. Biol. 215(1990):403-410) using the BLOSUM62 matrix, a gap existence penalty of 11, and a gap extension penalty of 1.

“Homologs”, as used herein, are to be considered as “variants” of the peptides of the present invention which have an amino acid sequence that differs by one or more amino acid residues from another related peptide having any one of the amino acid sequences SEQ ID No. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, or 41. The “variant” or “homolog” may have “conservative” amino acid changes, wherein a substituted amino acid has similar structural or chemical properties. One type of conservative amino acid substitutions refer to the interchangeability of residues having similar side chains. For example, a group of amino acids having aliphatic side chains is glycine, alanine, valine, leucine, and isoleucine; a group of amino acids having aliphatic-hydroxyl side chains is serine and threonine; a group of amino acids having amide-containing side chains is asparagine and glutamine; a group of amino acids having aromatic side chains is phenylalanine, tyrosine, and tryptophan; a group of amino acids having basic side chains is lysine, arginine, and histidine; and a group of amino acids having sulphur-containing side chains is cysteine and methionine. Preferred conservative amino acids substitution groups are: valine-leucine-isoleucine, phenylalanine-tyrosine, lysine-arginine, alanine-valine, and asparagine-glutamine. More rarely, a “variant” or “homolog” may have “non-conservative” changes (for example, replacement of a glycine with a tryptophan).

The “homologs” or “variants” of the present invention may have at least one, at least two, at least three, at least four, at least five, at least six, or seven amino acid change (substitution or deletion) compared to a peptide having any one of the amino acid sequences SEQ ID No. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, or 41. The “homologs” or “variants” of the present invention may have a maximum number of one, two, three, four, five, six or seven amino acid changes.

According to a preferred embodiment of the present invention the fragment of the peptides disclosed herein (SEQ ID No. 1 to 41) consist of 15 to 24, preferably 16 to 24, 17 to 24, 18 to 24, 19 to 24, 20 to 24, 21 to 24, 22 to 24, 23 to 24, 16 to 23, 17 to 23, 18 to 23, 19 to 23, 20 to 23, 21 to 23, 22 to 23, 16 to 22, 17 to 22, 18 to 22, 19 to 22, 20 to 22, 21 to 22, 16 to 21, 17 to 21, 18 to 21, 19 to 21, 20 to 21, 16 to 20, 17 to 20, 18 to 20, 19 to 20, 16 to 19, 17 to 19, 18 to 19, 16 to 18, or 17 to 18 amino acid residues, in particular of 15, 16, 17, 18, 19, 20, 21, 22, 23, or 24 amino acid residues.

Another aspect of the present invention relates to a method for detecting and/or quantifying human immunodeficiency virus (HIV) specific antibodies in a sample of a subject comprising the step of determining the presence and/or amount of antibodies binding to

a) a peptide consisting of the amino acid sequence AIVCTRPNNNTRKSIRIGPGQVFYT (SEQ ID No. 1), or

b) a homolog having at least 70% identity with a peptide of a), or

c) a fragment of a peptide of a) or b) consisting of 15 to 24 amino acid residues in said sample.

The presence of antibodies directed to HIV-derived peptides and/or polypeptides in a sample of a subject indicates that said subject has an HIV infection. The absence of antibodies directed to HIV-derived peptides and/or polypeptides in a sample of a subject indicates that said subject has no HIV infection.

A further aspect of the present invention relates to a method for detecting and/or quantifying human immunodeficiency virus (HIV) specific antibodies in a sample of a subject comprising the step of determining the presence and/or amount of antibodies binding to

a) a peptide consisting of the amino acid sequence AIVCTRPNNNTRKSIRIGPGQVFYT (SEQ ID No. 1), or

b) a homolog having at least 70% identity with a peptide of a), or

c) a fragment of a peptide of a) or b) consisting of 15 to 24 amino acid residues in said sample.

Yet another aspect of the present invention relates to a method for monitoring the progress of a human immunodeficiency virus (HIV) infection in a subject comprising the step of determining the amount of antibodies binding to

a) a peptide consisting of the amino acid sequence AIVCTRPNNNTRKSIRIGPGQVFYT (SEQ ID No. 1), or

b) a homolog having at least 70% identity with a peptide of a), or

c) a fragment of a peptide of a) or b) consisting of 15 to 24 amino acid residues in said sample.

Another aspect of the present invention relates to a method for monitoring the effects of treatment of a subject with an anti-HIV agent comprising the steps of:

(i) determining the amount of antibodies binding to

-   -   a) a peptide consisting of the amino acid sequence         AIVCTRPNNNTRKSIRIGPGQVFYT (SEQ ID No. 1), or     -   b) a homolog having at least 70% identity with a peptide of a),         or     -   c) a fragment of a peptide of a) or b) consisting of 15 to 24         amino acid residues in a sample of the subject prior to         administration of said anti-HIV agent,

(ii) determining the amount of antibodies binding to

-   -   a) a peptide consisting of the amino acid sequence         AIVCTRPNNNTRKSIRIGPGQVFYT (SEQ ID No. 1), or     -   b) a homolog having at least 70% identity with a peptide of a),         or     -   c) a fragment of a peptide of a) or b) consisting of 15 to 24         amino acid residues in a sample of the subject in one or more         post-administration samples of said subject,

(iii) comparing the amount of the determined antibodies in the sample of the subject prior to administration of said anti-HIV agent with the amount of the determined antibodies in the one or more post administration sample or samples, and

(iv) determining whether said anti-HIV agent influences the levels and/or isotypes of HIV-specific antibodies in said subject.

The peptides of the present invention can also be used to determine the presence of HIV specific antibodies in patients who are treated with an anti-HIV agent (e.g. antiretroviral agents). This allows to monitor and to determine whether an anti-HIV agent influences the levels and/or isotypes of HIV-specific antibodies in said subject. For instance, if the amount of HIV specific antibodies determined in step (ii) is lower (e.g. at least 10%, at least 20%, at least 50%, at least 80%) compared to step (i) the anti-HIV agent may positively influence the course of the disease because it may indicate that the HIV load is reduced. If, however, the amount of HIV specific anti-bodies determined in step (ii) is higher (e.g. at least 10%, at least 20%, at least 50%, at least 80%, at least 100%) compared to step (i) the anti-HIV agent may have no influence on the course of the disease and will most probably not be considered as being useful in the treatment of HIV infections.

In order to enhance the informative value of the methods of the present invention it is advantageous to determine further the presence of other antibodies which are able to bind to other polypeptides encoded by the HIV genome or to peptidic fragments thereof (e.g. to a peptide consisting of any one of SEQ ID Nos. 1 to 41)

According to a preferred embodiment of the present invention the presence and/or amount of antibodies binding to

a) a peptide consisting of the amino acid sequence LLGLWGCSGKLICTTAVHWNSSWSN (SEQ ID No. 2),

b) a homolog having at least 70% identity with a peptide of a), or

c) a fragment of a peptide of a) or b) consisting of 15 to 24 amino acid residues in a sample of the subject is further determined.

The peptide having amino acid sequence LLGLWGCSGKLICTTAVHWNSSWSN (SEQ ID No. 2) is derived from the HIV polypeptide gp41 (subtype C) which is part of the HIV envelope protein complex. Surprisingly, HIV infected subjects produce a significant amount of antibodies binding to this peptide or fragments thereof. Therefore the additional detection and/or quantification of such antibodies allows an even more powerful diagnosis of HIV infected subjects.

It is an unexpected finding that also peptide fragments derived from the envelope protein gp41 of HIV subtype C can be used to diagnose HIV infections of more than one, preferably of more than two, preferably of more than three, more preferably of more than four, more preferably of more than five, more preferably of more than six, more preferably of more than seven, even more preferably of more than eight, HIV subtypes since antibodies directed to gp41 of all of these subtypes and obtainable from subjects having an HIV infection bind to a peptide consisting of the amino acid sequence LLGLWGCSGKLICTTAVHWNSSWSN (SEQ ID No. 2) or a homolog or a fragment thereof consisting of 15 to 24 amino acid residues. Hence, the method of the present invention allows to diagnose HIV infections of HIV subtypes A, B, C, D, F, G, H, J and/or K, whereby the diagnosis of HIV subtypes B and C is most preferred.

Therefore a further aspect of the present invention relates to a method for diagnosing a human immunodeficiency virus (HIV) infection in a subject comprising the step of determining the presence of antibodies binding to

a) a peptide consisting of the amino acid sequence LLGLWGCSGKLICTTAVHWNSSWSN (SEQ ID No. 2), or

b) a homolog having at least 70% identity with a peptide of a), or

c) a fragment of a peptide of a) or b) consisting of 15 to 24 amino acid residues in a sample of the subject, and diagnosing an HIV infection in said patient when the presence of such antibodies in said sample is determined or diagnosing no HIV infection in said patient when the absence of such antibodies in said sample is determined. LLGLWGCSGKLICTTAVHWNSSWSN (SEQ ID No. 2) as well as its homologs and fragments thereof can also be used—according to a further aspect of the present invention—in a method for monitoring the effectiveness of treatment to a subject with an anti-HIV agent as defined above. Such methods can also be used in combination with a step of determining the presence of antibodies binding to a peptide consisting of the amino acid sequence AIVCTRPNNNTRKSIRIGPGQVFYT (SEQ ID No. 1) or a homolog or a fragment thereof consisting of 15 to 24 amino acid residues as defined above.

Another aspect of the present invention relates to a method for detecting and/or quantifying human immunodeficiency virus (HIV) specific antibodies in a sample of a subject comprising the step of determining the presence and/or amount of antibodies binding to

a) a peptide consisting of the amino acid sequence LLGLWGCSGKLICTTAVHWNSSWSN (SEQ ID No. 2), or

b) a homolog having at least 70% identity with a peptide of a), or

c) a fragment of a peptide of a) or b) consisting of 15 to 24 amino acid residues in said sample.

A further aspect of the present invention relates to a method for detecting and/or quantifying human immunodeficiency virus (HIV) specific antibodies in a sample of a subject comprising the step of determining the presence and/or amount of antibodies binding to

a) a peptide consisting of the amino acid sequence LLGLWGCSGKLICTTAVHWNSSWSN (SEQ ID No. 2), or

b) a homolog having at least 70% identity with a peptide of a), or

c) a fragment of a peptide of a) or b) consisting of 15 to 24 amino acid residues in said sample.

Yet another aspect of the present invention relates to a method for monitoring the progress of a human immunodeficiency virus (HIV) infection in a subject comprising the step of determining the amount of antibodies binding to

a) a peptide consisting of the amino acid sequence LLGLWGCSGKLICTTAVHWNSSWSN (SEQ ID No. 2), or

b) a homolog having at least 70% identity with a peptide of a), or

c) a fragment of a peptide of a) or b) consisting of 15 to 24 amino acid residues in said sample.

Another aspect of the present invention relates to a method for monitoring the effects of treatment of a subject with an anti-HIV agent comprising the steps of:

(i) determining the amount of antibodies binding to

-   -   a) a peptide consisting of the amino acid sequence         LLGLWGCSGKLICTTAVHWNSSWSN (SEQ ID No. 2), or     -   b) a homolog having at least 70% identity with a pep-tide of a),         or     -   c) a fragment of a peptide of a) or b) consisting of 15 to 24         amino acid residues in a sample of the subject prior to         administration of said anti-HIV agent,

(ii) determining the amount of antibodies binding to

-   -   a) a peptide consisting of the amino acid sequence         LLGLWGCSGKLICTTAVHWNSSWSN (SEQ ID No. 2), or     -   b) a homolog having at least 70% identity with a peptide of a),         or     -   c) a fragment of a peptide of a) or b) consisting of 15 to 24         amino acid residues in a sample of the subject in one or more         post-administration samples of said subject,

(iii) comparing the amount of the determined antibodies in the sample of the subject prior to administration of said anti-HIV agent with the amount of the determined antibodies in the one or more post administration sample or samples, and

(iv) determining whether said anti-HIV agent influences the levels and/or isotypes of HIV-specific antibodies in said subject.

According to a further preferred embodiment of the present invention the presence and/or amount of antibodies binding to

a) a peptide consisting of the amino acid sequence NALFYRSDIVPLEKNSSEYILINCN (SEQ ID No. 3), or

b) a homolog having at least 70% identity with a peptide of a), or

c) a fragment of a peptide of a) or b) consisting of 15 to 24 amino acid residues in a sample of the individual is further determined.

The peptide having the amino acid sequence NALFYRSDIVPLEKNSSEYILINCN (SEQ ID No. 3) is derived from the HIV polypeptide gp120 (subtype C).

According to a preferred embodiment of the present invention the presence and/or amount of antibodies binding to

a) a peptide consisting of the amino acid sequence GIKQLQARVLAIERYLKDQQLLGLW (SEQ ID No. 4), or

b) a homolog having at least 70% identity with a peptide of a), or

c) a fragment of a peptide of a) or b) consisting of 15 to 24 amino acid residues in a sample of the individual is further determined.

The peptide having the amino acid sequence GIKQLQARVLAIERYLKDQQLLGLW (SEQ ID No. 4) is derived from the HIV polypeptide gp41 (subtype C).

The fragments of all of these peptides or homologs having at least 70% identity to said peptides may consist of amino acid residues 1 to 24, 1 to 23, 1 to 22, 1 to 21, 1 to 20, 1 to 19, 1 to 18, 1 to 17, 1 to 16, 1 to 15, 2 to 24, 2 to 23, 2 to 22, 2 to 21, 2 to 20, 2 to 19, 2 to 18, 2 to 17, 2 to 16, 3 to 24, 3 to 23, 3 to 22, 3 to 21, 3 to 20, 3 to 19, 3 to 18, 3 to 17, 4 to 24, 4 to 23, 4 to 22, 4 to 21, 4 to 20, 4 to 19, 4 to 18, 5 to 24, 5 to 23, 5 to 22, 5 to 21, 5 to 20, 5 to 19, 6 to 24, 6 to 23, 6 to 22, 6 to 21, 6 to 20, 7 to 24, 7 to 23, 7 to 22, 7 to 21, 8 to 24, 8 to 23, 8 to 22, 9 to 24, 9 to 23, 2 to 25, 3 to 25, 4 to 25, 5 to 25, 6 to 25, 7 to 25, 8 to 25, 9 to 25, or 10 to 25 of SEQ ID. No. 1 to 41.

According to a particularly preferred embodiment of the present invention the presence and/or amount of antibodies binding to

a) a peptide consisting of the amino acid sequence WRSELYKYKVVEIKPLGIAPTKAKRRVVEREKR (SEQ ID No. 5), or

b) a homolog having at least 70% identity with a peptide of a), or

c) a fragment of a peptide of a) or b) consisting of 15 to 32 amino acid residues in a sample of the individual is further determined.

The peptide having the amino acid sequence WRSELYKYKVVEIKPLGIAPTKAKRRVVEREKR (SEQ ID No. 5) is derived from the HIV polypeptide gp120 (subtype C).

The fragments of this peptide of a homolog having at least 70% identity to said peptide may consist of amino acid residues 1 to 31, 1 to 30, 1 to 29, 1 to 28, 1 to 27, 1 to 26, 1 to 25, 1 to 24, 1 to 23, 1 to 22, 1 to 21, 1 to 20, 1 to 19, 1 to 18, 1 to 17, 1 to 16, 1 to 15, 2 to 32, 2 to 31, 2 to 30, 2 to 29, 2 to 28, 2 to 27, 2 to 26, 2 to 25, 2 to 24, 2 to 23, 2 to 22, 2 to 21, 2 to 20, 2 to 19, 2 to 18, 2 to 17, 2 to 16, 3 to 32, 3 to 31, 3 to 30, 3 to 29, 3 to 28, 3 to 27, 3 to 26, 3 to 25, 3 to 24, 3 to 23, 3 to 22, 3 to 21, 3 to 20, 3 to 19, 3 to 18, 3 to 17, 4 to 32, 4 to 31, 4 to 30, 4 to 29, 4 to 28, 4 to 27, 4 to 26, 4 to 25, 4 to 24, 4 to 23, 4 to 22, 4 to 21, 4 to 20, 4 to 19, 4 to 18, 5 to 32, 5 to 31, 5 to 30, 5 to 29, 5 to 28, 5 to 27, 5 to 26, 5 to 25, 5 to 24, 5 to 23, 5 to 22, 5 to 21, 5 to 20, 5 to 19, 6 to 32, 6 to 31, 6 to 30, 6 to 29, 6 to 28, 6 to 27, 6 to 26, 6 to 25, 6 to 24, 6 to 23, 6 to 22, 6 to 21, 6 to 20, 7 to 32, 7 to 31, 7 to 30, 7 to 29, 7 to 28, 7 to 27, 7 to 26, 7 to 25, 7 to 24, 7 to 23, 7 to 22, 7 to 21, 8 to 32, 8 to 31, 8 to 30, 8 to 29, 8 to 28, 8 to 27, 8 to 26, 8 to 25, 8 to 24, 8 to 23, 8 to 22, 9 to 32, 9 to 31, 9 to 30, 9 to 29, 9 to 28, 9 to 27, 9 to 26, 9 to 25, 9 to 24, 9 to 23, 10 to 32, 10 to 31, 10 to 30, 10 to 29, 10 to 28, 10 to 27, 10 to 26, 10 to 25, 10 to 24, 11 to 32, 11 to 31, 11 to 30, 11 to 29, 11 to 28, 11 to 27, 11 to 26, 11 to 25, 12 to 32, 12 to 31, 12 to 30, 12 to 29, 12 to 28, 12 to 27, 12 to 26, 13 to 32, 13 to 31, 13 to 30, 13 to 29, 13 to 28, 13 to 27, 14 to 32, 14 to 31, 14 to 30, 14 to 29, 14 to 28, 15 to 32, 15 to 31, 15 to 30, 15 to 29, 16 to 32, 16 to 31, 16 to 30, 17 to 32, 17 to 31, 2 to 33, 3 to 33, 4 to 44, 5 to 33, 6 to 33, 7 to 33, 8 to 33, 9 to 33, 10 to 33, 11 to 33, 12 to 33, 13 to 33, 14 to 33, 15 to 33, 16 to 33, 17 to 33, 18 to 33, or 19 to 33 of SEQ ID No. 5.

In some preferred embodiments the methods of the present invention involve the determination of the presence and/or amount of antibodies binding to more than one peptide, homolog or fragment as defined herein. Preferred combinations include the following peptides and its respective homologs and fragments as defined above: SEQ ID No. 1 with SEQ ID No. 2; SEQ ID No. 1 with SEQ ID No. 3; SEQ ID No. 1 with SEQ ID No. 4; SEQ ID No. 1 with SEQ ID No. 5; SEQ ID No. 2 with SEQ ID No. 3; SEQ ID No. 2 with SEQ ID No. 4; SEQ ID No. 2 with SEQ ID No. 5; SEQ ID No. 1 with SEQ ID No. 2 and SEQ ID No. 3; SEQ ID No. 1 with SEQ ID No. 2 and SEQ ID No. 4; SEQ ID No. 1 with SEQ ID No. 2 and SEQ ID No. 5; SEQ ID No. 2 with SEQ ID No. 3 and SEQ ID No. 4; SEQ ID No. 2 with SEQ ID No. 3 and SEQ ID No. 5; SEQ ID No. 1 with SEQ ID No.2, SEQ ID No. 3 and SEQ ID No. 4; SEQ ID No. 1 with SEQ ID No. 2, SEQ ID No. 3 and SEQ ID No. 5; SEQ ID No. 2 with SEQ ID No. 3, SEQ ID No.4 and SEQ ID No. 5; SEQ ID No. 1 with SEQ ID No.2, SEQ ID No.3, SEQ ID No. 4, and SEQ ID No. 5. Of course it is also possible to combine these combinations with at least one, two, three, four, five, six, seven, eight, nine, or ten of the peptides having SEQ ID No. 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, or 41.

According to a further preferred embodiment of the present invention the presence and/or amount of antibodies binding to HIV capsid protein p24 in a sample of the individual is further determined.

According to a particularly preferred embodiment of the present invention the presence and/or amount of antibodies binding to at least one polypeptide selected from the group consisting of HIV integrase, HIV reverse transcriptase+RNAse H, HIV protease and HIV matrix protein p17 in a sample of the individual is further determined.

The presence and/or amount of antibodies binding to a peptide or polypeptide in a sample can be determined using various methods. It is particularly preferred to use a method selected from the group consisting of enzyme-linked immunosorbent assay (ELISA), radioimmune assay (RIA), Western blot assay, dot blot assay, bead assay, peptide array and polypeptide array.

According to a particularly preferred embodiment of the present invention the sample of the subject is a sample selected from the group consisting of blood sample, serum sample, plasma sample, saliva, tears, urine, nose secret, genital secretion, stool and breast milk, whereby blood, serum or plasma samples are particularly preferred.

The sample taken from a subject suspected or known of having an HIV infection comprises a pool of antibodies of various sub-types directed to various epitopes of the polypeptides and peptides of the HIV. Therefore, according to a preferred embodiment of the present invention the antibodies to be determined and/or quantified are selected from the group consisting of IgG, IgG1, IgG2, IgG3, IgG4, IgA and IgM, wherein IgG and IgM are particularly preferred.

The presence and/or the amount of antibodies in a sample of a subject can be determined by using one single peptide or polypeptide as defined herein or by using more than one, preferably more than two, more preferably more than three, even more preferably more than four, of said peptides or polypeptides. This allows determining simultaneously the presence and/or amount of antibodies binding to different antigens and epitopes.

The peptides and proteins of the present invention can be added in liquid phase to a serum of an individual in order to pre-adsorb the antibodies comprised in the serum which are specific for or bind to at least one (preferably at least two, three, four, five, six, ten or even all) peptide and/or protein disclosed herein followed by the subsequent binding of the remaining free antibodies against the complete glycosylated antigens of the virus in order to determine the epitope specificity and portion of antibodies directed towards the peptide, sum of peptides or sum of peptides and proteins to obtain additional diagnostic and or prognostic information.

Another aspect of the present invention relates to a peptide consisting of the amino acid sequence selected from the group consisting of AIVCTRPNNNTRKSIRIGPGQVFYT (SEQ ID No. 1), LLGLWGCSGKLICTTAVHWNSSWSN (SEQ ID No. 2), RVRGILRNWPQWWIWGILGFWMIII (SEQ ID No. 6), WMIIICRGEENSWVTVYYGVPVWTE (SEQ ID No. 7), PVWTEAKTTLFCASDAKAYEKEVHN (SEQ ID No. 8), KEVHNVWATHACVPTDPSPQELVLE (SEQ ID No. 9), ELVLENVTESFNMWENDMVDQMHED (SEQ ID No. 10), QMHEDIIGLWDESLKPCVKLTPLCV (SEQ ID No. 11), TPLCVTLNCNTTSHNNSSPSPMTNC (SEQ ID No. 12), PMTNCSFNATTELRDKTQKVNALFY (SEQ ID No. 13), NALFYRSDIVPLEKNSSEYILINCN (SEQ ID No. 3), LINCNTSTITQACPKVSFDPIPIHY (SEQ ID No. 14), IPIHYCAPAGYAILKCNNKTFNGTG (SEQ ID No. 15), FNGTGPCSNVSTVQCTHGIKPVVST (SEQ ID No. 16), PVVSTQLLLNGSLAEGEIIIRSENL (SEQ ID No. 17), RSENLTDNAKTIIVHLNKSVAIVCT (SEQ ID No. 18), QVFYTNEIIGNIRQAHCNISRELWN (SEQ ID No. 19), RELWNNTLEQVKKKLKEHFQNKTIE (SEQ ID No. 20), NKTIEFQPPAGGDLEVTTHSFNCRG (SEQ ID No. 21), FNCRGEFFYCNTSNLFNITASNASD (SEQ ID No. 22), SNASDANNNTITLPCKIKQIINMWQ (SEQ ID No. 23), INMWQEVGRAMYAPPIAGNITCNSS (SEQ ID No. 24), TCNSSITGLLLTRDGGNNNDTGNNN (SEQ ID. No. 25), TGNNNDTEIFRPGGGNMKDNWRSEL (SEQ. ID. No. 26), AVGLGAVLLGFLGTAGSTMGAASIT (SEQ ID. No. 27), AASITLTVQARQLLSGIVQQQSNLL (SEQ ID No. 28), QSNLLRAIEAQQHMLQLTVWGIKQL (SEQ ID No. 29), GIKQLQARVLAIERYLKDQQLLGLW (SEQ ID No. 4), SSWSNKSQDYIWGNMTWMQWDREIN (SEQ ID No. 30), DREINNYTDIIYTLLEESQSQQEKN (SEQ ID No. 31), QQEKNEKDLLALDSWNNLWNWFSIT (SEQ ID No. 32), WFSITKWLWYIKIFIMIVGGLIGLR (SEQ ID No. 33), LIGLRIILGVLSIVKRVRQGYSPLS (SEQ ID No. 34), YSPLSFQTLPPNPRGPDRLRGIEEE (SEQ ID No. 35), GIEEEGGEQDKDRSIRLVSGFLALV (SEQ ID No. 36), FLALVWEDLRSLCLFSYHRLRDFIL (SEQ ID No. 37), RDFILIAGRAAELLGRSSLRGLQTG (SEQ ID No. 38), GLQTGWQALKYLGSLVQYWGLELKK (SEQ ID No. 39), and LELKKSAINLFDTTAIVVAEGTDRL (SEQ ID No. 40) or a fragment thereof consisting of 15 to 24 amino acid residues or consisting of the amino acid sequence WRSELYKYKVVEIKPLGIAPTKAKRRVVEREKR (SEQ ID No. 5) or a fragment thereof consisting of 15 to 32 amino acid residues or consisting of the amino acid sequence GTDRLIEGLQGIGRAIYNIPRRIRQGFEAALL (SEQ ID No. 41) or a fragment thereof consisting of 15 to 31 amino acid residues.

The peptides of the present invention can be synthetically produced by chemical synthesis methods which are well known in the art. Alternatively, the peptides may be coupled to a polypeptide carrier (e.g. Keyhole limpet hemocyanin) to augment their stability. Furthermore, they may be produced as recombinant fusion proteins together with a carrier molecule or coupled via known interactions (Biotin-Streptavidin-Avidin).

The polypeptides can be produced in a microorganism and then be isolated and if desired, further purified. The polypeptides can be produced in microorganisms such as bacteria, yeast or fungi, in eukaryote cells such as a mammalian or an insect cell, or in a recombinant virus vector such as adenovirus, poxvirus, herpesvirus, Simliki forest virus, baculovirus, bacteriophage, sindbis virus or sendai virus. Suitable bacteria for producing the compound/peptide include E. coli, B. subtilis or any other bacterium that is capable of expressing peptides. Suitable yeast types for expressing said compound/peptide include Saccharomyces cerevisiae, Schizosaccharomyces pombe, Candida, Pichia pastoris or any other yeast capable of expressing peptides. Corresponding methods are well known in the art. Also methods for isolating and purifying recombinantly produced polypeptides are well known in the art and include e.g. as gel filtration, affinity chromatography, ion exchange chromatography, etc.

To facilitate the isolation of the polypeptide, a fusion polypeptide may be made wherein the polypeptide is translationally fused (covalently linked) to a heterologous peptide or polypeptide which enables isolation by affinity chromatography. Typical heterologous peptides or polypeptides are His-Tag (e.g. His6; 6 histidine residues), GST-Tag (Glutathione-S-transferase) etc. The fusion polypeptide facilitates not only the purification of the peptide but may also prevent the degradation of said peptide during purification. If it is desired to remove the heterologous polypeptide after purification, the fusion polypeptide may comprise a cleavage site at the junction between the poly-peptide and the heterologous peptide or polypeptide. The cleavage site consists of an amino acid sequence that is cleaved with an enzyme specific for the amino acid sequence at the site (e.g. proteases).

The polypeptides used in the methods of the present invention (such as HIV capsid protein p24, HIV integrase, HIV reverse transcriptase+RNAse H, HIV protease and HIV matrix protein p17) are preferably recombinantly produced using methods known in the art.

Another aspect of the present invention relates to a solid support comprising one or more peptides as disclosed herein, wherein the solid support comprises

a) a peptide consisting of the amino acid sequence AIVCTRPNNNTRKSIRIGPGQVFYT (SEQ ID No. 1), or

b) a homolog having at least 70% identity with a peptide of a), or

c) a fragment of a peptide of a) or b) consisting of 15 to 24 amino acid residues immobilized thereon.

An alternative aspect of the present invention relates to a solid support comprising one or more peptides as disclosed herein, said solid support comprising

a) a peptide consisting of the amino acid sequence LLGLWGCSGKLICTTAVHWNSSWSN (SEQ ID No. 2), or

b) a homolog having at least 70% identity with a peptide of a), or

c) a fragment of a peptide of a) or b) consisting of 15 to 24 amino acid residues immobilized thereon.

An alternative aspect of the present invention relates to a solid support comprising one or more peptides as disclosed here-in for determining the presence or absence and/or the amount of antibodies binding to the human immunodeficiency virus (HIV) in sample, said solid support comprising

a) a peptide consisting of the amino acid sequence LLGLWGCSGKLICTTAVHWNSSWSN (SEQ ID No. 2), or

b) a homolog having at least 70% identity with a peptide of a), or

c) a fragment of a peptide of a) or b) consisting of 15 to 24 amino acid residues immobilized thereon.

These solid supports can be used in the methods of the pre-sent invention, e.g., in particular for

-   -   determining the presence or absence and/or the amount of         antibodies binding to the human immunodeficiency virus (HIV) in         a sample,     -   diagnosing a human immunodeficiency virus (HIV) infection in a         subject,     -   monitoring the course and progress of a human immunodeficiency         virus (HIV) infection in a subject     -   monitoring the effects of treatment on a subject with an         anti-HIV agent

or any other method involving the determination of antibodies binding to HIV.

A solid support of the present invention can be selected from the group consisting of glass, polystyrene, PVDF membrane, nylon, nitrocellulose, sepharose, and agarose.

The immobilization onto the solid support of the peptides and polypeptides of the present invention may be achieved by immobilizing them directly onto the solid support. Alternatively the peptides may be modified C- and/or N-terminally with a cysteine residue or other known moieties which allow immobilizing molecules on a solid support. Such immobilization may be effected by covalent or noncovalent binding. Such covalent or non-covalent binding onto a solid support may be performed by methods and by use of agents well known in the art.

According to a preferred embodiment of the present invention a peptide consisting of the amino acid sequence LLGLWGCSGKLICTTAVHWNSSWSN (SEQ ID No. 2) or AIVCTRPNNNTRKSIRIGPGQVFYT (SEQ ID No. 1), respectively, or a homolog as defined above or a fragment thereof consisting of 15 to 24 amino acid residues is further immobilized on said solid support.

According to another preferred embodiment of the present invention

a) a peptide consisting of the amino acid sequence NALFYRSDIVPLEKNSSEYILINCN (SEQ ID No. 3), or

b) a homolog having at least 70% identity with a peptide of a), or

c) a fragment of a peptide of a) or b) consisting of 15 to 24 amino acid residues is further immobilized thereon.

According to a particularly preferred embodiment of the present invention

a) a peptide consisting of the amino acid sequence GIKQLQARVLAIERYLKDQQLLGLW (SEQ ID No. 4), or

b) a homolog having at least 70% identity with a peptide of a), or

c) a fragment of a peptide of a) or b) consisting of 15 to 24 amino acid residues is further immobilized thereon.

According to another preferred embodiment of the present invention

a) a peptide consisting of the amino acid sequence WRSELYKYKVVEIKPLGIAPTKAKRRVVEREKR (SEQ ID No. 5), or

b) a homolog having at least 70% identity with a peptide of a), or

c) a fragment of a peptide of a) or b) consisting of 15 to 32 amino acid residues is further immobilized thereon.

The solid support of the present invention may comprise more than one peptide, homolog or fragment as defined above immobilized thereon. Preferred combinations of such molecules include the following peptides and its respective homo logs and fragments as defined above: SEQ ID No. 1 with SEQ ID No. 2; SEQ ID No. 1 with SEQ ID No. 3; SEQ ID No. 1 with SEQ ID No. 4; SEQ ID No. 1 with SEQ ID No. 5; SEQ ID No. 2 with SEQ ID No. 3; SEQ ID No. 2 with SEQ ID No. 4; SEQ ID No. 2 with SEQ ID No. 5; SEQ ID No. 1 with SEQ ID No. 2 and SEQ ID No. 3; SEQ ID No. 1 with SEQ ID No. 2 and SEQ ID No. 4; SEQ ID No. 1 with SEQ ID No. 2 and SEQ ID No. 5; SEQ ID No. 2 with SEQ ID No. 3 and SEQ ID No. 4; SEQ ID No. 2 with SEQ ID No. 3 and SEQ ID No. 5; SEQ ID No. 1 with SEQ ID No.2, SEQ ID No. 3 and SEQ ID No. 4; SEQ ID No. 1 with SEQ ID No. 2, SEQ ID No. 3 and SEQ ID No. 5; SEQ ID No. 2 with SEQ ID No. 3, SEQ ID No.4 and SEQ ID No. 5; SEQ ID No. 1 with SEQ ID No.2, SEQ ID No.3, SEQ ID No. 4 and SEQ ID No. 5. Of course it is also possible to combine these combinations with at least one, two, three, four, five, six, seven, eight, nine, or ten of the peptides having SEQ ID No. 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, or 41.

The solid support of the present invention may also comprise HIV-derived polypeptides. Therefore, according to a preferred embodiment of the present invention capsid protein p24 is further immobilized on said solid support.

According to another preferred embodiment of the present invention at least one polypeptide selected from the group consisting of HIV integrase, HIV reverse transcriptase+RNAse H, HIV protease and HIV matrix protein p17 is further immobilized thereon.

The solid support is used to immobilize one or more of the peptides and/or polypeptides of the present invention. Depending on the further use of the solid support said solid support may have various forms. The solid support is preferably provided in the form of a column, bead, test tube, microtiter dish, solid particular, microchip or membrane. Such solid supports can be used in various immunoassays.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is further illustrated by the following figures and examples, however, without being restricted thereto.

FIGS. 1A-C show antibody responses to HIV-1 clade C gp120 and gp120-derived peptides.

FIG. 1A shows frequency (y-axes: number of reactive sera) of IgG, IgG subclass, IgA and IgM responses of African (left) and European (right) patients to recombinant gp120 and 24 overlapping gp120 peptides (x-axes: peptides 1-24).

FIG. 1B shows position of overlapping gp120 peptides in gp120 of the HIV-1 clade C South African strain (clade C_ZA) and of the reference strain HXB2 (clade B_HXB2). Gaps (numbers of missing amino acids 20 are displayed) in gp120 from clade C and B required for optimal sequence alignment are indicated. Relevant protein domains de-scribed for gp120 clade B are indicated (SP: signal peptide, V1-V5: variable regions 1-5).

FIG. 1C shows multiple sequence alignment of the amino acid sequence of peptide 120/15 (SEQ ID No.: 1) of HIV-1 clade C South African strain (Ref.C.ZA) with corresponding peptides from HIV-1 reference strains. Percentages of sequence identity with the Ref. C.ZA peptides are indicated on the right margin. Dots are conserved amino acids, dashes are gaps, N-linked glycosylation sites are underlined. The numbering system refers to HIV-1 strain HXB2 (Ref.B.FR) and “aa” stands for amino acid.

FIGS. 2A-B show antibody responses to HIV-1 clade C gp41-derived peptides.

FIG. 2A shows frequency (y-axes: number of reactive sera) of IgG, IgG subclass, IgA and IgM responses of African (left) and European (right) patients to 17 overlapping gp41 peptides (x-axes: peptides 1-17).

FIG. 2B shows position of overlapping gp41 peptides in gp41 of the HIV-1 clade C South African strain (clade C_ZA) and of the reference strain HXB2 (clade B_HXB2). A gap (number of missing amino acids is displayed) in gp41 from clade B required for optimal sequence alignment is indicated. Relevant protein domains/epitopes described for gp41 clade B are indicated (F: fusion peptide, TM: transmembrane domain, ID: immunodominant region, IS: immunosuppressive region, MPER: membrane proximal external region).

FIGS. 3A-B show purity and immunoreactivity of recombinant HIV-1 clade C structural, accessory and pol-derived proteins.

FIG. 3A shows coomassie-stained SDS PAGE containing recombinant matrix (MA), capsid (CA), nucleocapsid (NC), NEF, TAT, VIF, protease (PR), reverse transcriptase+RNase H (RR), integrase (IN) and molecular weight markers (M). Molecular weights (kDa) are indicated on the left.

FIG. 3B shows frequency (y-axes: number of reactive sera) of IgG, IgG subclass, IgA and IgM responses of African (left) and European (right) patients to structural, accessory and pol-derived proteins (x-axes).

FIG. 4 shows IgG and IgM reactivity profiles to gp120-derived proteins and peptides of two individuals with negative results in established conventional HIV diagnostic tests. Shown are positive IgG and IgM antibody reactivities to HIV-1 clade C antigens (rgp120, MA: matrix; NEF, TAT, PR: protease, RR: reverse transcriptase+RNaseH, IN: integrase) and peptides. Negative test results obtained with the InnoLIA IgG immunoblot for HIV-1 antigens gp120, gp41, integrase (IN), capsid (CA), matrix (MA) and HIV-2 antigens gp105, gp36 are shown on the right margin.

FIG. 5A shows an amino acid sequence alignment showing identical amino acids (*), substitutions (·) and gaps (−). The peptide length is indicated on the right margin as number of amino acids. The peptides aligned in FIG. 5A are AIVCTRPNNNTRKSIRIGPGQVFYT (SEQ ID No. 1) and NTRKSIRIGPGQTFY (SEQ ID No. 42; see Casseb et al. Braz J Med Biol Res 3S (2002): 369-37S).

FIG. 5B shows the medium IgG serum reactivity towards the two peptides of FIG. 5A in African and European HIV-infected patients, expressed as optical density (OD) subtracted of the reactivity to the negative control.

FIG. 5C shows the frequency (y-axes: number of reactive sera) of IgG responses of African (left) and European (right) patients to peptides having SEQ ID No. 1 and 42.

DETAILED DESCRIPTION EXAMPLES Example 1

Materials and Methods:

Synthesis of HIV-1 Clade C Envelope Overlapping Peptides

Twenty-four and 17 peptides covering the complete amino acid sequences of gp120 and gp41 from the South African HIV-1 clade C reference strain (isolate ZA.04.04ZASK146, Los Alamos HIV sequence database accession no. AY772699), were produced by solid phase synthesis on a CEM-Liberty (CEM, USA) or Applied Biosystems peptide synthesizer (Life technologies, USA). All peptides were 25 amino acids long, except the gp120 and gp41 C-terminal peptides accounting for 33 and 32 amino acids respectively, and had an overlap of 5 amino acids (see the following table).

HIV-1 clade C Envelope Peptides:

Peptides Amino acid sequence SEQ ID No. Solvent gp120 peptides 120/1 RVRGILRNWPQWWIWGILGFWMIII  6 10% DMF 120/2 WMIIICRGEENSWVTVYYGVPVWTE  7 2% DMSO, 1 mM DTE 120/3 PVWTEAKTTLFCASDAKAYEKEVHN  8 PBS, 1 mM DTE 120/4 KEVHNVWATHAVPTDPSPQELVLE  9 H20, 1 mM DTE 120/5 ELVLENVTESFNMWENDMVDQMHED 10 H20, 9 mM NaOH 120/6 QMHEDIIGLWDESLKPCVKTLPLCV 11 H20, 1 mM DTE 120/7 TPLCVTLNCNTTSHNNSSPSPMTNC 12 5% ACN, 1 mM DTE 120/8 PMTNSFNATTELRDKTQKVNALFY 13 H20, 1 mM DTE 120/9 NALFYRSDIVPLEKNSSEYILINCN  3 2% DMSO, 3 mM NaOH, 1 mM DTE 120/10 LINNTSTITQAPKVSFDPIPIHY 14 5% DMSO, 1 mM DTE 120/11 IPIHYCAPAGYAILKCNNKTFNGTG 15 H20, 1 mM DTE 120/12 FNGTGPSNVSTVQTHGIKPVVST 16 H20, 1 mM DTE 120/13 PVVSTQLLLNGSLAEGEIIIRSENL 17 3 mM NaOH 120/14 RSENLTDNAKTIIVHLNKSVAIVCT 18 H20, 1 mM DTE 120/15 AIVCTRPNNNTRKSIRIGPGQVFYT  1 H20, 1 mM DTE 120/16 QVFYTNEIIGNIRQAHCNISRELWN 19 5% DMF, 1 mM DTE 120/17 RELWNNTLEQVKKKLKEHFQNKTIE 20 H20 120/18 NKTIEFQPPAGGDLEVTTHSFNCRG 21 H20, 1 mM DTE 120/19 FNCRGEFFYCNTSNLFNITASNASD 22 PBS, 2 mM NaOH, 120/20 SNASDANNNTITLPCKIKQIINMWQ 23 H20 120/21 INMWQEVGRAMYAPPIAGNITCNSS 24 10% ACN, 1 mM DTE 120/22 TCNSSITGLLLTRDGGNNNDTGNNN 25 H20, 1 mM DTE 120/23 TGNNNDTEIFRPGGGNMKDNWRSEL 26 H20 120/24 WRSELYKYKVVEIKPLGIAPTKAKRRVVEREKR  5 H20 gp41 peptides 41/1 AVGLGAVLLGFLGTAGSTMGAASIT 27 5% ACN 41/2 AASITLTVQARQLLSGIVQQQSNLL 28 5% DMF, 1 mM Acetic acid 41/3 QSNLLRAIEAQQHMLQLTVWGIKQL 29 H20 41/4 GIKQLQARVLAIERYLKDQQLLGLW  4 H20 41/5 LLGLWGCSGKLICTTAVHWNSSWSN  2 5% DMSO, 1 mM DTE 41/6 SSWSNKSQDYIWGNMTWMQWDREIN 30 H20, 3 mM NaOH 41/7 DREINNYTDIIYTLLEESQSQQEKN 31 H20, 6 mM NaOH 41/8 QQEKNEKDLLALDSWNNLWNWFSIT 32 H20, 3 mM NaOH 41/9 WFSITKWLWYIKIFIMIVGGLIGLR 33 2% DMSO 41/10 LIGLRIILGVLSIVKRVRQGYSPLS 34 10% ACN 41/11 YSPLSFQTLPPNPRGPDRLRGIEEE 35 H20 41/12 GIEEEGGEQDKDRSIRLVSGFLALV 36 H20 41/13 FLALVWEDLRSLC-LFSYHRLRDFIL 37 5% DMF 41/14 RDFILIAGRAAELLGRSSLRGLQTG 38 H20 41/15 GLQTGWQALKYLGSLVQYWGLELKK 39 5% ACN 41/16 LELKKSAINLFDTTAIVVAEGTDRL 40 2% DMSO, 2 mM NaOH 41/17 GTDRLIEGLQGIGRAIYNIPRRIRQGFEAALL 41 2% DMF

The synthesis was performed with the 9-fluorenyl-methoxy-carbonyl (Fmoc)-method, using PEG-PS preloaded resins. Synthesized peptides were washed with dichloromethane, cleaved from the resins in a mixture of 19 ml trifluoroacetic acid, 500 ul silane and 500 ul H20 and precipitated into tertbutylmethylether. Peptides were separated from by-products by reverse-phase HPLC in an acetonitrile gradient (UltiMate 3000 Pump, Dionex, USA) to a purity >90% and their identity was verified by mass spectrometry (Microflex MALDI-TOF, Bruker, USA). The peptides' chemical features were predicted by ProtParam on the Expasy proteomics server and were considered in the optimization of the solubilization conditions. Highly hydrophobic peptides were solubilized in dimethylformamide (DMF), dimethylsulfoxide (DMSO) or acetonitrile (ACN), while reducing agents such as dithioerythritol (DTE) were added to peptides rich in Cysteins and NaOH to strongly acidic peptides.

Expression and Purification of Recombinant HIV-1 Clade C Proteins

Recombinant matrix (MA), capsid (CA), nucleocapsid (NC) proteins as well as accessory NEF, TAT and VIF and the pol-derived protease (PR), reverse transcriptase+RNAseH (RR) and integrase (IN) were expressed in Escherichia coli (E. coli). Briefly, the cDNA sequences of the structural and accessory proteins as well as of the protease were derived from the HIV-1 clade C reference strain from South Africa (isolate ZA.04.04ZASK146, Los Alamos HIV sequence database accession no. AY772699). The reverse transcriptase-RNAseH and the integrase constructs were derived from the Ethiopian HIV-1 clade C isolate ET.86.ETH2220 (Los Alamos HIV sequence database accession no. U46016). The cDNA of the proteins, followed by a hexa-histidine tag, was codon-optimized for bacterial expression and cloned into a pET17b vector (ATG:biosynthetics, Germany). Expression of the recombinant proteins in E. coli BL21 (DE3) cells, grown to an OD600=0.4−0.6 in LB medium supplemented with l O Omg/l ampicillin, was induced by addition of 0.5-1.0 mM isopropyl-β-thiogalactopyranoside (IPTG) and proteins were purified by Nickel-affinity chromatography under native or denaturing conditions. For purification under native conditions of matrix, capsid and nucleocapsid proteins, cells were lysed in 50 mM NaH2PO4, 300 mM NaCl, 10 mM Imidazole pH 8.0, PMSF (1 μl/ml), Lysozyme (1 mg/ml) by sequential cycles of freezing and thawing; DNA was cleaved by treatment with 5 μg/ml DNaseI (20 min at room temperature); and, after removal of cellular debris (by centrifugation at 18000 rpm, 20 min, 4° C.), the clear lysate was incubated with Nickel-agarose (QIAGEN, Germany) 2-4 h at 4° C. Elution of the His-tagged proteins was performed with an imidazole gradient (20, 50, 100, 250 mM Imidazole) in 50 mM NaH2PO4, 300 mM NaCl pH 8.0. For purification of NEF, TAT and protease under denaturing conditions, cells were lysed in 8M Urea or 6M Guanidinium chloride buffer for at least 2 h or overnight at room temperature. After removal of cellular debris (by centrifugation at 18000 rpm, 20 min, 4° C.) and incubation of the clear lysate with Nickel-agarose (QIAGEN, Germany) (2-4 h at room temperature or overnight at 4° C.), a pH gradient (pH 6.3, 5.6, 4.5) was used to elute the recombinant proteins in 8M Urea, 100 mM NaH2PO4, 10 mM Tris. For purification of recombinant integrase, the cells were first lysed under native conditions as described above, and, since after centrifugation (18000 rpm, 20 min, 4° C.) the protein was found in the insoluble fraction, this was resuspended in 8M Urea, 100 mM NaH2PO4, 10 mM Tris, pH 8.0 and incubated at room temperature overnight. After removal of cellular debris (by a second step of centrifugation at 18000 rpm, 20 min, 4° C.), the recombinant integrase was purified under denaturing conditions in 8M Urea as described above. Purification of VIF and reverse transcriptase+RNAse was achieved by using an inclusion body preparation protocol. Removal of urea and refolding of the recombinant proteins purified under denaturing conditions were achieved by sequential dialysis steps.

The identity of the proteins was verified by SDS-PAGE and Coomassie staining (FIG. 3A) as well as by Westernblot and by mass spectrometry. Their secondary structure and thermal stability were analyzed by Circular dichroism spectroscopy on a Jasko J-810 spectropolarimeter (Japan Spectroscopic, Japan). The biochemical features of the recombinant HIV-1 clade C proteins, predicted with the ProtParam software on the Expasy server and assessed experimentally as described above, are outlined in the following table.

Biochemical Features of Recombinant HIV-1 Clade C Proteins:

Migration MW 2 SOS-PAGE Secondary Thermal Proteins 1 kDa kDa pI 4 structure4 Stability 5 MA 15.5 17.5 9.1 α-helical > Tm = 65° C. β-sheet CA 26.5 24.0 6.6 α-helical Tm = 66° C. NC 7.2 11.0 10.2 β-sheet < n.d. random coil NEF 24.6 30.0 6.2 α-helical & n.d. β-sheet TAT 12.2 17.0 9.0 Random coil n.d. VIF 23.7 24.0 10.5 β-sheet > Tm > 95° C. α-helical PR 11.7 12.0 8.7 β-sheet & Tm = 55° C. random coil RR 65.1 65.0 6.8 α-helical & Tm > 95° C. β-sheet IN 33.2 33.5 7.4 α-helical & n.d. β-sheet ₁Protein abbreviations: MA: matrix, CA: capsid, NC: nucleocapsid, PR: protease, RR: reverse transcriptase+RNAseH, IN: integrase. ₂MW: Molecular weight in kilo Daltons (kDa), as predicted with ProtParam and verified by mass spectrometry. ₃pI: Isoelectrical point predicted with ProtParam. ₄Secondary structure: determined by circular dichroism spectroscopy, predominance of alphahelical or beta-sheet elements. ₅Thermal stability: determined by circular dichroism spectroscopy; Tm: melting temperature; n.d.: not done.

Study Subjects and Routine Immunoassays

Sera were taken from 14 African HIV-infected patients, from 2 highly exposed African individuals, from 15 European HIV-infected patients and from 10 uninfected individuals. HIV sero-positivity and -negativity was confirmed for each of the subjects by routine analyses. HIV-specific IgG immunoblots were carried out by Line Immuno Assay (InnoLIA, Innogenetics, Bel-gium) and asymptomatic subjects were additionally tested with the Abbott Murex HIV Ag/Ab combination (Abbott, USA).

HIV-1 Clade C Specific IgG, IgA and IgM Determinations by ELISA

ELISA plates (Nunc Maxisorp, Thermo Fisher Scientific, USA) were coated overnight at 4° C. with the HIV-1 clade C derived peptides and proteins diluted in 100 mM sodium bicarbonate buffer pH 9.6 (2 ug/ml). After washing in PBS, 0.05% v/v Tween20 and blocking in 2% w/v BSA, PBS, 0.05% v/v Tween20 for at least 4 h at room temperature, the plates were incubated with sera diluted 1:200 in 0.5% w/v BSA, PBS, 0.05% v/v Tween20 overnight at 4° C. Bound antibodies were detected with mouse anti-human IgG1, IgG2, IgG4, IgA, IgM (BD, 1:1000, 2 h at room temperature) or mouse anti-human IgG3 (1:5000, 2 h at room temperature, Sigma Aldrich, St. Louis, Mo.) and horseradish peroxidase (HRP)-coupled sheep anti-mouse IgG (1:2000, 1 h at room temperature, GE Healthcare, Waukesha, Wis.). Total IgG antibodies were detected with a directly labelled HRP-anti human IgG (1:5000, 1 h at room temperature, GE Healthcare, USA). The color reaction was induced with 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) di-ammonium salt and the optical density (OD405 nm-OD490 nm) was measured on a Spectra Max spectrophotometer (Molecular Devices, USA). As control antigen for the analysis of envelope-specific reactivity, we used recombinant His-tagged gp120 from HIV-1 clade C, isolate CN54, expressed in 293 cells (#11233-VO SH, Sino Biological, China). For interplate normalization we analyzed on each plate a positive control serum specific for each antibody isotype/subclass. Additionally, reactivity of each serum sample to human serum albumin (HSA) was tested as negative control. Coating of the antigens was verified by detection of His-tagged proteins with a mouse anti-His-tag antibody (Dianova, Germany) and by detection of untagged proteins and peptides with a pool of HIV-infected sera. Unspecific binding of the detection antibodies to coated antigens was excluded by buffer control analyses. All determinations were carried out as duplicates and results are shown as normalized means of the raw data subtracted by the reactivity to the negative control antigen. Cut-off values were calculated for each antibody isotype/subclass and for each antigen as the mean+3SD of the results of the HIV uninfected subjects.

Sequence Alignments

For multiple sequence alignments, the amino acid sequence identity was calculated with ClustalW2 on the EMBL-EBI server and alignments were generated with the program Gene Doc. Sequences are numbered accordingly to the international HXB2 numbering scheme, with amino acid insertions carrying the number of the last corresponding HXB2 amino acid followed by sequential letters.

Results

Almost Identical IgG, IgA and IgM Responses Towards gp120 Epitopes from HIV-1 Clade C in HIV-Infected Patients from Africa and Europe

For a detailed epitope mapping of gp120, sera from HIV-1-infected patients from Zimbabwe were tested, where clade C is the predominant HIV-1 subtype, and from European patients infected with HIV-1 strains from different clades for antibody reactivity with recombinant gp120 and 24 gp120-derived overlapping peptides. These peptides covered the complete amino acid sequence of gp120 derived from the South African HIV-1 subtype C reference strain (FIG. 1A, B). IgG, IgA, IgM and IgG1-4 subclass reactivities were measured.

Interestingly, IgG, IgG subclass, IgA and IgM response pro-files towards the peptides were almost identical in the African (FIG. 1A, left panel) and in the European (FIG. 1A, right panel) HIV-infected patients. The recognition pattern of the peptides was similar for all antibody classes and the IgG subclasses. However, the analysis of antibody levels and frequencies of recognition showed that IgG and in particular IgG1 responses dominated in both populations. Peptide 120/15 was the major antibody-reactive peptide in terms of frequency and intensity of recognition for the African and European patients (FIG. 1A). Peptide 120/24 was also recognized by a majority of the individuals tested. The overview of gp120 (FIG. 1B) shows that peptide 120/15 resides in the V3 domain, which is supposed to contain a binding site for the co-receptor CCR5/CXCR4 on CD4 cells. Pep-tide 120/24 is located at the very C-terminal end of gp120.

FIG. 1C contains a sequence alignment of peptide 120/15 with the corresponding peptides in various HIV-1 reference strains from different continents. A considerable degree of sequence variation of the peptide 120/15-corresponding regions was found among the strains, ranging from 88 to 72% sequence identity. De-pending on the strain, the peptide 120/15-defined region contains one or two N-linked glycosylation sites.

African and European Patients Recognize Highly Similar Epitopes on gp41 from HIV-1 Clade C

Next, the IgG, IgA and IgM responses of the African and European patients to 17 overlapping peptides derived from HIV-1 clade C gp41 was analyzed (FIGS. 2A, B). Again it was found that the African and European patients recognized similar peptides and that the immune response was dominated by IgG and in particular by IgG1 antibodies. Both the frequency and the intensity of recognition were lower towards the gp41 peptides than to the gp120-derived peptides. IgG and IgG1 antibodies were directed mainly to a region defined by peptides 41/4-8 (FIG. 2A). This region includes areas, which have been designated as “immunosuppressive” and “immunodominant” domains and contain the majority of the predicted N-linked glycosylation sites of gp41 (FIGS. 2A, B). Interestingly, the other antibody-reactive area defined by peptides 41/14-17 was located at the C-terminal portion of gp41, which is part of the so-called “cytoplasmic domain”.

African and European HIV-Infected Patients React Primarily with Structural and Pol-Derived but not with Accessory Proteins

In order to characterize the antibody response directed to viral proteins other than the surface antigens, HIV-1 clade C structural, pol-derived and accessory proteins were expressed in E. coli and purified and the protein-specific antibody levels were measured in African (FIG. 3B, left panel) and European sera (FIG. 3B, right panel). Similar as for the envelope proteins, the immune response was dominated by IgG and in particular by IgG1 antibodies. Again patients of both populations showed a similar recognition profile: The protease, reverse transcriptase+RNAseH, integrase, as well as the capsid protein and the matrix protein were the most frequently and strongly recognized antigens. Antibody responses towards the nucleocapsid protein and the accessory proteins were rare and low.

IgG Subclass Recognition of HIV Proteins and Peptides is Indicative of Mixed Th1/Th2 Immune Response

The measurements of IgG subclass responses towards the gp120 and gp41 peptides as well as against the structural, poi-derived and accessory proteins were performed using the same serum dilution. Since IgG1 represents the dominating IgG subclass, IgG1 responses were more intense and frequent than IgG2, IgG3 and IgG4 responses. However, the antigen and epitope recognition profile was similar for all subclasses in the African and European patients. The frequencies and intensities of IgG2 and IgG4 responses were comparable, which is indicative of a mixed Th1/Th2 immune response.

High Sensitivity and Specificity of Diagnostic Tests Based on Recombinant Proteins and Peptides Assembling the Clade C Proteome

The comprehensive analysis of antibody responses showed that the panel of HIV-1 clade C-derived antigens and peptides allowed the reliable detection of specific IgG antibodies in each of the HIV-infected patients from Africa and Europe. No false positive test results were obtained when sera from uninfected individuals were tested. Peptide 120/15 was as good as complete rgp120 for IgG-based diagnosis of HIV-infected patients because it allowed identifying 29 out of the 29 patients. Likewise, peptide 41/5 allowed identifying 29 out of 29 patients whereas peptide 120/24 was positive in 21 patients. Testing for IgG reactivity to the capsid protein identified 29/29, to reverse transcriptase+RNAseH 27/29, to integrase 27/29 and to protease 26/29 patients. Peptides 120/15 and 41/5 can therefore be used alone to diagnose HIV infections in individuals. Using a panel of peptides 120/15, 120/24, rgp120, capsid and pol-derived proteins each of the infected patients was diagnosed by IgG testing.

Furthermore, it was found that HIV-highly exposed African individuals with an infection, who were negative in routine antigen/IgG+IgM determinations (Abbott Murex HIV Ag/Ab combination, Abbott, USA) as well as in Immunoblot-based assays (InnoLIA, Innogenetics, Belgium; shown in FIG. 4, right margin), could be diagnosed by IgG and IgM testing to the panel of HIV-1 clade C-derived antigens and peptides (FIG. 4).

Example 2

In this example the reactivity of the peptides having the amino acid sequence AIVCTRPNNNTRKSIRIGPGQVFYT (SEQ ID No. 1; u120/15″) and NTRKSIRIGPGQTFY (SEQ ID No. 42; “Cons C”, see Casseb et al. Braz J Med Biol Res 35 (2002): 369-375) with serum of HIV infected individuals is examined. The results of this example are depicted in FIG. 5.

FIG. 5A shows a comparison of the amino acid sequences of peptide 120/15 and the consensus peptide Cons C used by Casseb et al. 2002, which has been made to incorporate a Threonine in position 13 to resemble the sequences of most of the subtype C sequences, whereas 120/15 contains a Valine in this position. Despite the fact that the sequence of the consensus peptide was modified to resemble the amino acid sequence of most of the sub-type C sequences, 11 out of 29 HIV-positive serum samples did not react with this peptide and hence were false negative in the diagnostic test, whereas peptide 120/15 allowed to identify each of the 29 HIV-positive serum samples (see Fig. SC).

Materials and Methods

The peptide “Cons C” which was used by Casseb et al. 2002, was manufactured using solid phase peptide synthesis, as described for the gp120-derived peptides (see example 1). For ELISA experiments the peptides were solubilized in H20, and the immunological assays were performed as described for the gp120-derived peptides (see example 1). 

The invention claimed is:
 1. A method for detecting or quantifying human immunodeficiency virus type 1 (HIV-1) specific antibodies in a sample of a subject, the method comprising the steps of: a) immobilizing one or more peptides or polypeptides on a solid support, wherein said peptides consist of an amino acid sequence selected from the group consisting of SEQ ID NOs: 1-5; b) contacting the solid support with the sample under conditions that permit antigen-antibody binding; and, c) detecting antigen-antibody binding through radioimmune assay (RIA), enzyme-linked immunosorbent assay (ELISA), Western blot assay, dot blot assay, bead assay, or peptide array assay.
 2. The method according to claim 1, wherein a) is the peptide consisting of the amino acid sequence SEQ ID NO.
 2. 3. The method according to claim 1, wherein a) is the peptide consisting of the amino acid sequence SEQ ID NO.
 3. 4. The method according to claim 1, wherein a) is the peptide consisting of the amino acid sequence SEQ ID NO.
 4. 5. The method according to claim 1, wherein a) is the peptide consisting of the amino acid sequence SEQ ID NO.
 5. 6. The method according to claim 1, wherein further the presence or amount of antibodies binding to human immunodeficiency virus (HIV) capsid protein p24 in a sample of the individual is determined.
 7. The method according to claim 1, wherein further the presence or amount of antibodies binding to at least one polypeptide selected from the group consisting of human immunodeficiency virus (HIV) integrase, HIV reverse transcriptase+RNAse H, HIV protease and HIV matrix protein p17 in a sample of the individual is determined.
 8. The method according to claim 1, wherein the sample of the subject is a sample selected from the group consisting of blood sample, serum sample, plasma sample, saliva, tears, urine, nose secret, genital secretion, stool and breast milk.
 9. The method according to claim 1, wherein the antibodies to be determined and/or quantified are selected from the group consisting of IgG, IgG1, IgG2, IgG3, IgG4, IgA and IgM, wherein IgG is particularly preferred. 